The present invention relates to a device for sealing an annular opening between an inner part, preferably a shaft, and an outer part surrounding said inner part, said parts being rotatable in relation to each other.
The sealing device according to the invention is especially suitable for complicated sealing applications, such as sealing arrangements for shafts and other movable elements operating in polluted atmosphere containing abrasive particles, or applications wherein a shaft extends through a wall and the difference between the pressures on opposite sides of the wall is substantial. Usually the sealing devices for such difficult sealing cases are complicated and expensive and have a short life.
A previously known sealing device for sealing an annular space between a shaft and a housing surrounding the shaft comprises a sealing element positioned in the annular opening and being constituted by a sleeve manufactured from an elastic material, usually rubber. The sleeve is sealingly connected with the housing, and to the interface between the sleeve and the shaft there is supplied a fluid, for example air or water, at a pressure which is higher than the pressures in the spaces at each side of the sleeve. Thereby there is provided a clearance space between the sleeve and the shaft, said space being filled with fluid which makes the friction between the sealing device and the shaft almost negligible, the fluid escaping into the spaces at each side of the sealing device thereby preventing connection between said spaces. In a sealing device of this kind the elasticity of an elastic material sleeve is takes advantage of, as the sleeve provides because of its elasticity a suitable clearance space between the sealing element and the shaft. However, it is a drawback that the rubber sleeve is easily damaged and does not stand high temperatures.
Thus, it is the object of the present invention to provide an improved sealing device of the kind described above.